Researchers at the University of Nevada (UNR) and at the Centers for Disease Control (CDC) will collaborate in an investigation of the epidemiology of a new hantavirus isolated from humans and rodents (peromyscus maniculatus) in the southwestern U.S. Preliminary studies indicate that in random sampling between 15-20% of P. maniculatus in Nevada contain antibody against this virus. Furthermore, human cases have been detected in Nevada. UNR has several assets important in these investigations. These include a P3 facility which will be used for the biocontainment studies, a virology group with experience in investigations of the epidemiology of epizootic diseases and with strong ties to researchers at the CDC and a strong biodiversity center with expertise in geographic instrumentation systems. Because of the geographic location of UNR to isolated areas containing high populations of the apparent host of the virus, P. maniculatus, field studies can be designed to examine the natural ecology and epidemiology of the disease. UNR also has the experience to carry out nested PCR and sequence analysis of biology samples from the study areas under P3 containment levels. The CDC identified the hantavirus responsible for the disease in the southwest. The director of the molecular component of these studies Dr. Nichol recently moved to CDC from UNR. Several of the investigators that will be part of these studies are employed by UNR at CDC or have moved from the CDC to UNR. This promotes strong interaction between the two groups. The investigators from the CDC have had extensive experience in virus diagnosis, epidemiology and pathogenesis. Additionally the CDC has a P4 facility which will be used to study details of the pathogenesis of the infection in native rodents. The study design will have four specific aims. 1) The identification of microenvironments important in the transmission of the virus. 2) The use of long term catch and release study areas to identify epidemiologic factors important in transmission of the virus. 3) Identification of the genetic diversity of the hantavirus associated with this new virus isolate. and 4) Laboratory studies designed to identify pathogenic factors important in the pathogenesis of the virus. The results of these investigations will allow us to better understand the potential danger that emerging pathogens have to human populations.